Wireless terminals for communication such as terminals are also known as e.g. User Equipments (UE), mobile terminals, wireless terminals and/or mobile stations. Terminals are enabled to communicate wirelessly in a cellular communications network or wireless communication system, sometimes also referred to as a cellular radio system or cellular networks. The communication may be performed e.g. between two terminals, between a terminal and a regular telephone and/or between a terminal and a server via a Radio Access Network (RAN) and possibly one or more core networks, comprised within the cellular communications network.
Terminals may further be referred to as mobile telephones, cellular telephones, laptops, or surf plates with wireless capability, just to mention some further examples. The terminals in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the RAN, with another entity, such as another terminal or a server.
The cellular communications network covers a geographical area which is divided into cell areas, wherein each cell area being served by a base station, e.g. a Radio Base Station (RBS), which sometimes may be referred to as e.g. “eNB”, “eNodeB”, “NodeB”, “B node”, Base Transceiver Station (BTS), or AP (Access Point), depending on the technology and terminology used. The base stations may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. A cell is the geographical area where radio coverage is provided by the base station at a base station site. One base station, situated on the base station site, may serve one or several cells. Further, each base station may support one or several communication technologies. The base stations communicate over the air interface operating on radio frequencies with the terminals within range of the base stations. In the context of this disclosure, the expression Downlink (DL) is used for the transmission path from the base station to the mobile station. The expression Uplink (UL) is used for the transmission path in the opposite direction i.e. from the mobile station to the base station.
In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), base stations, which may be referred to as eNodeBs or even eNBs, may be directly connected to one or more core networks.
Universal Mobile Telecommunications System (UMTS) is a third generation mobile communication system, which evolved from the GSM, and is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. UMTS Terrestrial Radio Access Network (UTRAN) is essentially a radio access network using wideband code division multiple access for terminals. The 3GPP has undertaken to evolve further the UTRAN and GSM based radio access network technologies.
3GPP LTE radio access standard has been written in order to support high bitrates and low latency both for uplink and downlink traffic. All data transmission is in LTE controlled by the radio base station.
Continuous Tracing of UEs in LTE and Systems
In a cellular network it is important to monitor the performance of involved network elements to end users such as UEs, to assure a quality to the end user. It is also important to be able to troubleshoot problem once they have been identified. A powerful tool for the monitoring and especially troubleshooting in cellular networks are the so called Traffic Traces, i.e. the ability to trace traffic events and/or reports in the network nodes involved in the data traffic to and from the UE. There are several different functions defined related to Traffic Traces by 3GPP:
Signalling based subscriber and equipment trace, also referred to as UE Trace, where a specific UE, identified by its International Mobile Subscriber Identity (IMSI) or International
Mobile Equipment Identity (IMEI), is traced. This means that signaling to and from the UE and additional node internal information related to the specific UE is gathered by the involved network nodes in both Core Network (CN) and RAN.
Cell traffic trace, also referred to as Cell Trace or Area Based Trace, where similar logging of data is done as in UE Trace but where the UEs to be measured on are decided based on that they are connected to certain specified radio network cells.
Minimization of Drive Test (MDT), which is an extension of signalling based subscriber and equipment trace and cell traffic trace where it is possible to order the UE to send measurements, e.g. to add the UE perspective on performance.
FIG. 1a is a view of a number of management interfaces in a Public Land Mobile Network (PLMN) according to 3GPP 32.101 v11.1.0.
A number of management interfaces in the PLMN is depicted in FIG. 1 such as:
1) Between Network Elements (NEs) and an Element Manager (EM) of a single PLMN Organisation. A network element is a manageable logical entity uniting one or more physical devices. This allows distributed devices to be managed in a unified way using one management system. The term network element means a facility or equipment used in the provision of a telecommunications service. Such term also includes features, functions, and capabilities that are provided by means of such facility or equipment, including subscriber numbers, databases, signalling systems, and information sufficient for billing and collection or used in the transmission, routing, or other provision of a telecommunications service. A PLMN is a regulatory term in telecommunications. A PLMN is a network that is established and operated by an administration or by a Recognized Operating Agency (ROA) for the specific purpose of providing land mobile telecommunications services to the public.
2) Between the EM and a Network Manager (NM) of a single PLMN Organisation;
NOTE: In certain cases the EM functionality may reside in the NE in which case this interface is directly from the NE to the NM. These management interfaces are given the reference name Itf-N and are a primary target for standardization. Itf-N is a standardized name of an Interface, Interface North. It is the interface between an NM and an Domain Manager (DM). Itf-P2P is a standardized name of an Interface, peer to peer, it is the interface between DMs.
3) Between the NM and the Enterprise Systems of a single PLMN Organisation.
4) Between the NMs of a single PLMN Organisation.
4a) Between Domain Managers (DMs) of a single PLMN Organisation.
5) Between Enterprise Systems & Network Managers of different PLMN Organisations.
5a) Between the DMs of different PLMN Organisations.
6) Between NEs.
Main traffic Interfaces in 3GPP nodes are illustrated in FIG. 1b, wherein
Ift P2P is the interface between Operations Support Systems (OSS) Core and Operation Support System for Radio & Core (OSS-RC),
S11 is the interface between Serving GPRS Support Node (SGSN) and a Mobility Management Entity (MME),
Radio Access Network Application Part (RANAP) is the interface between SGSN and Radio Network Controller (RNC), and
S1AP is the interface between an MME and an eNB, and
X2AP is the interface between two eNBs.
From an operator perspective, there are some problems:
For Area based tracing, standardization assumes that all UEs that are capable to be measured on shall be included in the trace scope. i.e. UEs to be measured on are decided based on that they are connected to certain specified radio network cells.
To trace all UEs over a large area generates a huge amount of data. One method to reduce data is to sample which UEs to be traced within an area. This is sometimes called UE Fraction, i.e. NEs may select a subset of all UEs that shall be traced. This method is not standardized in 3GPP. This leads to that when a UE enters a new NE, it is random if the area based tracing shall continue for the UE if an UE Fraction was used to select a subset of UEs.
For Subscriber tracing such as e.g. UETR, the solution is very Radio Access Technology (RAT) specific, such as one solution for LTE and one for WCDMA.